Fast coating compositions and methods

ABSTRACT

A method of providing an anticorrosive coating includes applying a first curable liquid layer to the associated substrate, the first layer having a thickness of at least about 100 micrometers, wherein the first layer includes at least one polymer or at least one monomer, quasi-one-dimensional particles or quasi-two-dimensional particles, sacrificial metal particles, and a solvent, wherein a percolation threshold of the particles is not reached in the presence of the solvent, wherein the percolation threshold of the particles is reached when between about 1% and about 20% of the solvent evaporates, applying a second curable liquid layer having a thickness of at least 100 micrometers on the top of the first layer after the percolation threshold of the particles is reached and viscosity of the first layer increases more than 50%, and allowing the first layer and the second layer to cure simultaneously.

I. BACKGROUND

Anticorrosive coatings often contain several layers. One of the mostcommonly used industrial coatings is a three-layer coating consisting ofzinc rich primer, an intermediate layer, and a topcoat. Currently,two-layer, and up to five-layer, coatings are also being used.

Typically, the primer is applied to the substrate, and allowed topartially cure, often so that the primer appears to be dry and can betouched. Then the process is repeated, until all the layers have beenapplied. This method may be called wet-on-dry (WoD) method. This oftenmeans that one layer per day may be applied. Spraying is the mostcommonly favored application method for WoD.

Wet-on-wet (WoW) is a technique in which wet layers are applied topreviously administered wet layers. Due to the consistency, most wetuncured coatings cannot have a second wet layer sprayed on top of them;especially for a vertical surface. There are many problems associatedwith the WoW method. First, sagging may be extensive. Sagging is often aproblem with a single layer, and is exponentially more difficult ifanother wet layer is added on an existing wet layer. The velocity of thespray creates significant momentum toward the substrate, which may leadto partial penetration of the previous wet layer. This can createserious problems if two different types of polymer systems, such asepoxies and polyurethanes, are used in consecutive layers. There may bea chemical problem if two different epoxies are used, because thestoichiometry may be too different. The same issue applies topolyurethanes. The problem is more pronounced if layers have differentpolymerization chemistries, such as amino-cured epoxies andpolyurethanes. Di-isocyanates in the polyurethane layer may reactextensively with the amines in the epoxy layer. Although a moderatecross reaction between the layers is desirable, because adhesion betweenthe layers is increased, excessive reaction might distort thestoichiometry so much that the polymerization will be incomplete in bothlayers.

Wet on wet coating has been used, for example, in the fabrication ofphotographic films. However, in that case the film is horizontal andmoves horizontally. The momentum of the liquid in that case is almostparallel to the film, thereby reducing the mixing of the layers.

Wet on wet coating has also been used for the coating of cars (e.g.US20040028822, Continuous process for applying a tri-coat finish on avehicle). The application is directed to a process and materials forcoating a substrate with a flake or other effect pigment containingtri-coat color finish in a continuous wet-on-wet application process. Inwater, hydrogen bonding is very important. When water evaporates, evenpartially, hydrogen bonding between constituents increases theviscosity.

Despite the significant success in the car industry, the WoW method hasnot been applied in field conditions, and especially not in oil and gasfields. First, cars already have an anticorrosive dry coating beforethey enter the final painting stage. Thus, the anticorrosive coatingdoes not get diluted with the subsequent layers. In oil and gas fields,and many other instances, the anticorrosive coating is the primer. Anydilution of the primer may be detrimental to its performance. Thisapplies to anticorrosive coatings that have sacrificial metal particles.These must be in electrical contact with each other and the substrate.Second, the thickness of the layers is typically more than 100 μm.Putting two wet layers on top of each other may result in considerablesagging. While it is aesthetically undesirable, it also gives unevencoating and performance.

Liquid coating materials should have a low enough viscosity so that theycan be sprayed, brushed, or otherwise readily applied. On the otherhand, the viscosity should be high enough that there is no sagging onvertical surfaces. The suitable viscosity application range is betweenabout 1000 cP (centipoise) and about 2500 cP, but can be between about1500 cP and about 2000 cP. Sagging may be prevented by making thecoating thin enough, and letting it dry before the next layer isapplied. This may make the whole coating process slow and expensive.Thixotropic additives may be used to increase the viscosity. Theseadditives are beneficial, but they have limits, and do not allow for theWoW method of the present teachings.

Conventional coating methods have several drawbacks. Despite the correctstoichiometry and proper mixing, one or more components may partiallyseparate, and be squeezed out from the interior of the coating layer.This may be harmful to the adhesion with the substrate and adhesionbetween the layers. When the curing agent is an amine, this phenomenonis called amine blush. The amine will further absorb water and carbondioxide on to the surface, leading to amine bloom that is more extensivethan amine blush. All this will have a negative effect on the binding ofthe next layer, and on the overall performance of the coating. All theseproblems may be alleviated by the present teachings. First, there is notime for the curing induced separation of the components. Consequently,there will not be any significant absorption of water and carbondioxide. Second, because there is a thin mixing layer, and the layersare cured at the same time, the polymer will be continuous without anyinterface, i.e., there may be a high density of intermingled polymerchains connecting two consecutive layers. In conventional methods therewill also be some bonding between layers, but the density is low, ifpolymerization has been mostly completed. Amine blush or bloom worsensthe situation when conventional coating methods are used. Excess amineacts as a polymerization terminator for epoxies and polyurethanes,preventing chemical bonding between the layers.

Evonik developed a method utilizing a new curing agent that willincrease the viscosity quickly. The drawbacks are a short pot life andthe use of a plural spray system.

The present teachings alleviate both of these drawbacks.

II. SUMMARY

The present teachings use the concept of a percolation threshold toadjust the viscosity of the liquid coating, so the mixing of the layersand sagging is minimized. Percolation traditionally means filteringfluids through porous materials. However, in materials science andphysical chemistry it also means a continuous pathway along a material.Percolation threshold is a concentration of particles in a medium, inwhich the particles are continuously touching each other so that theyform a continuous network. If these particles are electricallyconducting, and the medium is not, a sudden increase of conductivity, asa function of the concentration of particles, indicates the percolationthreshold. Other physical properties may also change abruptly when thepercolation threshold is reached. Viscosity may be a sensitive indicatorof the percolation threshold.

Percolation depends strongly on the shape of the particles. Sphericalparticles have a high percolation threshold, about 30 vol %. It is to beunderstood that “spherical” is to be understood as an approximate shape,and not an exact geometric sphere. A high aspect ratio lowers thepercolation threshold dramatically. Quasi-one-dimensional particles,such as CNTs (carbon nanotubes), may have a percolation threshold under1 vol %. Platelets, such as graphene, may have a percolation thresholdunder 10 vol %. When a liquid contains spherical, quasi-two-dimensional,and quasi-one-dimensional, particles, as is often the case in thematerials of the present teachings, the percolation threshold is foundby experimentation. For example, 30 vol % of zinc particles is about 75wt %, because zinc has a density of about 7 g/cm³. Thus, current zonerich primers have about 80 wt % of zinc, because zinc to zinc contact isuseful for an anticorrosive function.

The present teachings avoid the problems of coating vertical stationarysubstrates, by adding quasi-one-dimensional, and quasi-two-dimensional,particles, such as carbon nanotubes (CNTs), graphene, zinc flakes, orglass flakes into the coating. These particles have a low percolationthreshold, such that the viscosity increases suddenly when thepercolation threshold is reached, for example, due to evaporation of asolvent. CNTs may be single walled (SWNT), double walled (DWNT), ormultiwalled carbon nanotubes (MWNT). Graphene may be single layer ormultilayer graphene. Also, fast evaporating solvents, such as t-butylacetate, may be used. After the solvent has evaporated the viscosity ofthe coating material is immediately very high, resembling partiallycured conventional coating materials. Extensive mixing of the layers mayfurther be avoided by a proper choice of components. One layer mayconsist primarily of aliphatic compound, while the other may consistmostly of aromatic compounds. One layer may also contain fluorinatedcompounds.

Epoxy-amine systems, especially at low temperatures and humidenvironments, have serious problems called amine blush and amine bloom.During, and immediately after, the curing process the surface may becomecontaminated by excess amine, water, and/or carbon dioxide. Sometimesthe freshly cured surface must be washed and sanded, otherwise theadhesion of the next layer may be adversely affected. Both amine blushand amine bloom can be avoided by the present teachings on the primerand intermediate layers (i.e., in all layers that are important for theanticorrosive properties).

These additives and compositions allow application of a second wet layeron top of the first wet layer, i.e., enabling the WoW method. Thetwo-layer coating of the present teachings competes favorably withconventional three-layer coatings in anticorrosive properties. Moreover,it can be applied in one day, while application of the three-coat systemmay take three days. Thus, the present teachings provide materials andmethods that can give considerable economic benefit.

The present teachings provide materials and methods for the fast coatingof surfaces by two or more different liquid layers that can be cured atthe same time. 10016 In one aspect of the present teachings, the surfaceis coated with a first wet coating material that containsquasi-one-dimensional particles or quasi-two-dimensional particles, andthen with a second wet coating material before the first wet coatingmaterial is cured.

In one aspect of the present teachings, the method may be used in oil orgas fields for the coating of equipment, such as oil rigs and pipes.

Another aspect of the present teachings is providing materials andmethods that avoid amine blush and bloom in the primer and allintermediate layers, especially in humid conditions, such as off-shoreenvironments.

Other benefits and advantages will become apparent to those skilled inthe art to which it pertains upon reading and understanding of thefollowing detailed specification.

III. DEFINITIONS

WoD (wet on dry)—a liquid layer applied on top of a dry layer.

WoW (wet on wet)—a liquid layer applied on top of a wet layer.

Quasi one-dimensional—one dimension of a particle is at least 50 timeslarger than the other two dimensions. For example, if MWNT has adiameter of 10 nm, and is more than 500 nm long, it is classified asquasi one-dimensional in this context. For simplicity, these particlesare called one-dimensional in the Description.

Quasi two-dimensional—two dimensions of a particle are at least 50 timeslarger than one dimension. For example, if a glass flake has a thicknessof 1 μm and is more than 50 μm wide in two dimensions, it is classifiedas quasi two-dimensional in this context. For simplicity, theseparticles are called two-dimensional in the Description.

Percolation threshold—the concentration of particles, wherein theparticles form a continuous three-dimensional network. The measure inthis context of the percolation threshold is viscosity, i.e., viscositywill increase significantly after percolation threshold is reached. Thisdefinition may give higher percolation threshold for some particles thanother methods, for example, CNTs electrical conductivity may indicatethat CNTs reach percolation threshold at very low concentrations, below0.1%, while the viscosity stays very low. Also in the present teachings,many different kinds of particles may participate in percolationnetwork.

Curable liquid—a polymer solution or melt that solidifies when a solventevaporates or temperature is ambient; or a monomer, or monomer mixture,that solidifies as a result of a polymerization reaction.

Wet coating layer—a wet layer whose thickness can be measured with astandard wet thickness contact gauge.

IV. FIGURES

The present teachings are described hereinafter with reference to theaccompanying drawings.

FIG. 1 shows a conventional two-coat method, wherein A is the substrate,B is the first layer applied to the substrate, C is the first layercured, D is the second layer applied on the substrate, and E is thesecond layer cured;

FIG. 2 shows the two-coat method of the present teachings, wherein A isthe substrate, B is the first layer applied to the substrate, C is thesecond layer applied to the substrate, and D is the first and secondlayer cured;

FIG. 3 shows the experimental viscosity (in KU units) of a coatingmaterial of Example 2, when solvent (VOC) is added in small portions;and

FIG. 4. Evaporation of the solvent from 125 micrometers thick layer ofmaterial of Example 1.

V. DETAILED DESCRIPTION

FIG. 1 depicts a method for the fabrication of a conventional two-coatsystem (WoD), in which the first layer is cured before a second layer isapplied. Often the first layer must be washed, and sanded before thesecond layer is applied, even if it freshly cured. This step is notincluded in FIG. 1, because it is not always mandatory.

FIG. 2 depicts the method of the present teachings (WoW). The firstlayer is applied, and before the first layer is cured, the second layeris applied. Thus, there is at least one less step. Also, no washing orsanding of the first layer is done in this method. Thus, there may betwo steps less than in the conventional method of FIG. 1. These extrasteps included in the conventional method are slow, and often only onelayer can be applied in one day.

Conventional coating systems have three layers, while the presentteachings may provide equal or better performance with just two layers.Conventional coating may take up to three days, while the coatingaccording to present teachings may be performed in one day. Thematerials and methods of the present teachings offer considerablesavings, and equal or better performance compared to the conventionalcoating materials and methods.

Coating compositions of the present teachings may contain polymer ormonomer(s), thixotropic agent, sacrificial metal particles, solvent, andquasi-one dimensional, and quasi-two-dimensional materials, such asgraphitic material, glass flakes, and mica. In one aspect of the presentteachings, the graphitic materials can be CNTs or graphene. Sacrificialmetal particles may be nickel, zinc, aluminum, or magnesium, or alloyscontaining these metals. These particles may be spherical or essentially2D flakes. These are non-limiting examples. All particles and materialsmay be functionalized so that they bind with the polymer matrix, otherparticles, or the substrate.

The polymer may be polyacrylate, polycarbonate, or polystyrene. Themonomer may be bisphenol A diglycidyl ether (BPDGE), Novolac (polymer ofBPDGE and formaldehyde), SU-8 (cyclic tetramer of BPDGE andformaldehyde, available from MicroChem® of Massachusetts), or anyhydrogenated or fluorinated form of these. These are non-limitingexamples, and numerous other di- and polyepoxies are known in the art.The thixotropic agents may be diamines, dithiols, amino thiols,carboxylic anhydrides, diphenols, or Mannich curing agents. These mayalso contain more than two functional groups. Specific, non-limitingexamples are 1,4-diaminobutane, 1,3-diamino-1-methyl cyclohexane,1,3-di(aminomethylene)benzene, and diamino polyethyleneoxide.

Polyurethanes, polyurethane-ureas, or polyureas may be fabricated fromdiisocyanates, polyisocyanates, polyols, or polyamines. Polyisocyanatesinclude, but are not limited to ethylene diisocyanate, 1,2-propylenediisocyanate, cyclohexane-1,3-diisocyanate, 4,4′-dicycloheylmethanediisocyanate, toluene diisocyanate, m-phenylene diisocyanate,3,3′-dimethyl-4,4′-biphenylene diisocyanate, and naphthalenediisocyanate. Diisocyanates may be modified by carbodiimide. Polyols maybe, for example, ethylene glycol, glycerol, polyester polyols,polycaprolactone polyols, polycarbonate polyols, polyethylene glycol, orpolypropylene glycol.

One-dimensional and two-dimensional materials are used to adjustviscosity, along with the proper choice of solvent, so that the materialcan be easily applied, but does not sag while the solvent evaporates.One-dimensional and two-dimensional materials have a low theoreticalpercolation threshold, between about 0.01 vol % to about 2 vol %, whilespherical three-dimensional particles have a percolation threshold ofabout 30 vol %. These values may be obtained if the dispersion of theparticles is perfect. However, many of these particles may aggregate, sothat the percolation threshold may be much bigger, for example, about0.1 vol % to about 20 vol % for quasi-one-dimensional andquasi-two-dimensional particles. Low percolation threshold is the reasonwhy quasi-one-dimensional and quasi-two-dimensional particles are wellsuited for the control of viscosity, preventing sagging, and preventingthe mixing of the layers. In one aspect of the present teachings,quasi-one dimensional particles can have a concentration between about0.1 to about 2 wt % (inclusive), quasi-two dimensional particles canhave a concentration between about 2 to about 20 wt % (inclusive), andthree dimensional particles can have a concentration between about 50 toabout 80 wt % (inclusive).

The composition may be adjusted so that the percolation threshold is notreached when a solvent is present, but is reached when the solvent evenpartially evaporates. When the particles form a continuous network, theviscosity may increase suddenly and significantly (more than 50%), andthere will be no sagging, even when a second wet layer is applied on thetop of the first wet layer. The increase of the viscosity may be muchmore than 50%.

FIG. 3 shows the viscosity of the primer (Example 2) as a function ofthe solvent concentration. The material of the Example 2 is denoted byan arrow, i.e., this material contains 13 wt % of solvent. FIG. 4 showsthe relative weight of 5 mil thick coating on 4″×4″ steel plate as afunction of time. At the beginning the weight is 100 wt % but decreasesfast. In about 20 minutes the weight is 97% of the original (3% of thesolvent has evaporated), and after six hours (360 minutes) about 8.5 wt% of total coating has evaporated. Because there is about 13 wt % of thesolvent at the beginning in the coating, and percolation threshold is at12% of the solvent, the percolation threshold will be reached when 3% ofthe weight is lost. This will take less than 20 minutes according toFIG. 4. In FIG. 4 the time axis is only 6-7 hours, but it can beestimated that all solvent has essentially evaporated in 10 hours, andmaximum viscosity is reached.

FIG. 4 depicts the viscosity of the coating material of Example 2 as afunction of added solvent (VOC). Diamond symbols represent measuredvalues, and squares are linear least squares fit. As can be seen in FIG.4, the viscosity first decreases very fast, with the slope of −415 cP/I% VOC. At around 13% VOC the slope changes to −93 cP/I % VOC. Thus, theslope is 4.5 times greater when the percolation threshold has beenreached.

EXAMPLES Example 1

Multiwalled carbon nanotubes (25 g) and nanographite (25 g) weredispersed into 5 kg of Epon™ 828 (an undiluted clear difunctionalbisphenol A/epichlorohydrin derived liquid epoxy resin) using a highspeed (10,000 rpm) blade mixer. Mixing was continued and 7.5 kg of zincpowder was added. Finally, 0.4 kg t-butyl acetate, 0.5 kg petroleumspirits, and 1.2 kg xylene were added. Four kilograms of this mixturewas mixed with 0.38 kg of Ancamide® 702B75 (a low viscosity, solventbased polyamide adduct curing agent, supplied at 75% solids inn-butanol). This mixture is the coating material for the first layer(primer) in Example 4 and was used immediately after fabrication.

Example 2

Multiwalled carbon nanotubes (25 g) and nanographite (25 g) weredispersed into 5 kg of Epon™ 828 using high speed (10,000 rpm) blademixer. Mixing was continued, and 7.5 kg of zinc powder was added.Finally, 0.3 kg t-butyl acetate, 0.3 kg petroleum spirits, and 0.8 kgxylene was added. Five kilograms of this mixture was mixed with 0.50 kgof Ancamide® 702B75 (Airproducts). t-Butyl acetate/Xylene 3:4 mixturewas added in measured portions (between about 25 g and about 100 g), andthe viscosity was measured after each addition. The result is shown inFIG. 3.

Example 3

The 5 g sample of the mixture of Example 1 was spread on a 4″×4″substrate using a 5 mil drawdown bar. The total weight of the substrateand coating was measured every minute for the first ten minutes, thenevery five minutes for the next twenty minutes, then every ten minutesfor the next thirty minutes, then hourly for the next five hours, andthen daily. The result of the first 6 hours is shown in FIG. 4.

Example 4

100 g of t-butyl acetate and 120 g Hi Sol® 10 (a naphthenic aromaticsolvent) were added to 1 kg of Epon™ 828. Similarly, 125 g of t-butylacetate, and 150 g Hi Sol® 10 were added into 1.05 kg of Aradur® 283 (aformulated polyamidoamine hardener). Both mixtures were mixed with eachother, and the final mixture constitutes the coating material for thesecond layer (topcoat) in Example 3, and was used immediately afterfabrication.

Example 5

The mixture of Example 1 was sprayed with a Binks® Trophy Series II2GXpaint gun using a Binks® 1.4 liquid nozzle tip, an LVMP air tip, and aBinks® 1.5-gal pressure pot. Steel substrates were 10 cm×20 cm and weresandblasted to SP10 standard (near-white metal blast cleaning fromSociety for Protective Coatings). A 200 μm thick layer was sprayed onthese panels in a vertical position. The solvent was allowed toevaporate for 20 minutes, and the second epoxy layer was sprayed onusing the material of Example 2 with the same equipment, but using a 1.0liquid tip, and an HVLP air tip. The thickness of the second layer (topcoat) was 150 μm. The coating was allowed to cure one week. Adhesion wastested using a PosiTest AT-A (DeFelsko) adhesion meter, and the resultwas 2240 psi.

Example 6

The primer of Example 1 was mixed with Ancamide 2767 in the ratio 10:1.This mixture contains 75 wt % Zn calculated of solids, and 2 wt % ofMWNTs of epoxy. Solvents comprise about 13 wt % of the total. About a 5mil to about a 12 mil (125 to 300 micrometers) layer of this mixture wassprayed using a cup gun (3M Accuspray gun) with 1.8 mm nozzle. After 10to 30 minutes of drying the epoxy topcoat containing 1 wt % CNTs wassprayed similarly. When the total wet coat was 20 mil, no sagging wasobserved. After curing at ambient temperature for one week there was noamine blush, blisters, or mud cracking observed.

The material of Example 1 is representative of the present teachings. Itcontains 13.2% solvents (VOC). The freshly fabricated material ofExample 2 contains 9.4% solvents. This material was used for theviscosity studies depicted in FIG. 3. These materials are denoted as E1and E2 in FIG. 3. The dotted line represents the percolation thresholdat 13% solvents.

Another aspect of the present teachings is the proper choice ofsolvents. Low boiling point solvents are used, which evaporate quicklyafter the paint is applied to the substrate. On the other hand, thesolvents should not interfere with the curing process. Thus, in oneaspect of the present teachings, no ketones are used. Alkanes, ethers,and esters may have low boiling points. These include hexane,cyclohexane, diethyl ether, ethyl propyl ether, ethyl acetate, andt-butyl acetate. When health effects and commercial availability areincluded, hexane, cyclohexane, a mixture of aliphatic hydrocarbons(mineral spirits or petroleum ether), or t-butyl acetate are chosen.When used with resins and curing agents, additional solvents, such asaromatic hydrocarbons or high boiling ethers, such as ethylene glycol,diethylene glycol dimethyl ether, or dimethyl phthalate may be used.

The material of Example 1 was applied to the surface, as explained inExample 3. The evaporation of the solvent was measured for severalhours. The evaporation was very fast in the beginning (see FIG. 3).Almost 30% of the solvent evaporated within the first fifteen minutes,and almost half evaporated within thirty minutes.

When the material E1 is applied on a surface, for example a 125 μmlayer, the solvent starts to evaporate. During the first minute, thesolvent concentration drops below 13%, i.e., the percolation thresholdis reached within one minute. After 28 minutes the solvent concentrationis about 9%, i.e., an additional 4% of the solvent has evaporated, andthe composition E2 is reached. On average, an additional 1% of thesolvent will be evaporated in 7 minutes, and the viscosity will increaseat the same time to 415 cP. This immediate and fast increase of theviscosity enables the WoW method of the present teachings.

Graphitic material may be SWNTs, DWNTs, MWNTs, monolayer or multilayergraphene, graphite, or functionalized forms of these. Graphitic materialmay be dispersed into any polymeric component, or into all of them, forexample, into both epoxy and amine. Dispersion methods includemechanical mixing, such as milling, high speed blades, ball milling,ultrasonic mixing, or hydrodynamic injection. Graphitic material may beexfoliated and cut during dispersion and may be chemically bound with amonomer or polymer simultaneously, especially in the presence ofcatalysts. The concentration of the CNTs may be between about 0.05 vol %and about 5 vol %, or in another aspect of the present teachings,between about 0.2 vol % and about 1.5 vol %, and the concentration ofgraphene, or graphite, may be between about 1 vol % and about 20 vol %.

Glass flakes may be used to increase viscosity and reduce the mixing ofthe consecutive coating layers during and after the application. Thebarrier properties of the cured coating will also be improved. Glassflakes may be silyl coated. Mica flakes may be similarly used. Theamount of glass or mica flakes may be between about 1 vol % and about 40vol %, or in another aspect of the present teachings between about 10vol % and about 30 vol %.

The primer may contain sacrificial metal particles, including aluminum,magnesium, zinc, titanium, iron, and nickel. Sacrificial metal should beless noble than the substrate (i.e. the sacrificial metal has a lowerreduction potential than the substrate). These particles may be nearlyspherical or platelets, and in some cases may be rods. Sacrificial metalparticles may have a concentration between about 10% and about 75%. Ifthe sacrificial metal particles are flakes, their concentration can bebetween about 10% and about 50%.

One method to reduce the viscosity of a coating material is to addsolvent that has a low enough boiling point, such as methyl ethylketone, n-butyl acetate, t-butyl acetate, alkanes, or arylalkanes, suchas octane, nonane, decane, toluene, or xylene that have boiling pointsbelow 200° C. The amount of volatile organic compounds (VOC) should bekept as low as possible, and in one aspect of the present teachings, theVOC are below 25%.

The coating material may be applied by any painting method, includingbrush, roller, spraying, and soaking. Spraying may be air pressurepowered, airless, plural spray, ultrasonic spray, or some other spray.The mixture may be heated or cooled during spraying. The spraying methodchosen sets some limits for the viscosity, mainly so that viscosity isnot too high, i.e., the concentration of the components in the paintshould not exceed the percolation threshold.

Most of the solvent will evaporate in less than one hour, and possiblywithin 15-30 minutes. Curing will start immediately after mixing, butfull cure may take several days. The surface may appear dry afterseveral hours and is suitable for conventional WoD application. However,in many cases it is not possible to apply the first and second layerduring the same day using the conventional WoD method. The coatingmaterials and methods of the present teachings allow the application ofthe second layer as soon as most of the solvent has evaporated from thefirst layer, i.e., when the first layer is still wet. This WoW methodwill allow coating of the substrate with two or more layers within oneday. This will significantly reduce the cost of coating. Also, bondingof the layers may be stronger than in conventional WoD coating.

Mixing of the consecutive layers may be reduced, and essentiallyavoided, if polarities of the mixtures are different. This may beachieved by making the first mixture essentially aliphatic, and thesecond essentially aromatic. Still another differentiation may beachieved by using fluorinated compounds that may be immiscible with bothaliphatic and aromatic compounds. Also, the solvent may be chosen sothat it is poorly miscible with the previous layer. Total immiscibilitybetween consecutive layers is not necessary. Immiscibility may reversemixing that may happen during spraying, or other coating method, so thatthe process resembles self-stratifying in the vicinity of the interface.

The primer and all intermediate layers have the composition of thepresent teachings when wet surfaces are coated. The topcoat may alsohave the composition of the present teachings, but that is notmandatory, because sagging and mixing of layers may not be problem.

In another aspect of the present teaching, after the anticorrosivecoating is applied, a self-stratifying coating can be applied on top,creating a three layer coating.

Clause 1—A method of coating an associated substrate with ananticorrosive coating, the method includes applying a first curableliquid layer to the associated substrate, the first curable liquid layerhaving a thickness of at least about 100 micrometers, wherein the firstcurable layer includes at least one polymer or at least one monomer,quasi-one-dimensional particles or quasi-two-dimensional particles,sacrificial metal particles, and a solvent, wherein a percolationthreshold of the quasi-one-dimensional particles or thequasi-two-dimensional particles is not reached in the presence of thesolvent, wherein the percolation threshold of the quasi-one-dimensionalparticles or the quasi-two-dimensional particles is reached when betweenabout 1% and about 20% of the solvent evaporates, and applying a secondcurable liquid layer having a thickness of at least 100 micrometers onthe top of the first curable liquid layer after the percolationthreshold of the quasi-one-dimensional particles or thequasi-two-dimensional particles is reached and viscosity of the firstcurable liquid layer increases more than 50%.

Clause 2—The method of clause 1, wherein the method further includesallowing the first curable liquid layer and the second curable liquidlayer to cure simultaneously.

Clause 3—The method of clauses 1 or 2, wherein the at least one monomeris at least two monomers, wherein one of the at least two monomerscontains at least two epoxy groups, wherein one of the at least twomonomers contains carboxylic anhydride, wherein one of the at least twomonomers contains any combination of the following: amino, thiol,phenolic hydroxyl.

Clause 4—The method of clauses 1-3, wherein the coating absorbssubstantially no water or carbon dioxide, and wherein the polymer willbe continuous without any interface.

Clause 5—The method of clauses 1-4, wherein the first curable liquidlayer contains quasi-one-dimensional particles and quasi-two-dimensionalparticles.

Clause 6—The method of clauses 1-5, wherein the quasi-one-dimensionalparticles have a concentration between about 0.1 weight percent andabout 2.0 weight percent, and the quasi-two-dimensional particles have aconcentration between about 2.0 weight percent and about 20 weightpercent.

Clause 7—The method of clauses 1-6, wherein the at least one polymerforms polyurethane, polyurea, or a mixture of the two, when allowed tocure.

Clause 8—The method of clauses 1-7, wherein the quasi-one-dimensionalparticles or quasi-two-dimensional particles are chosen from graphiticparticles, carbon nanotubes, graphene, glass flakes, or mica, whereinthe solvent contains methyl ethyl ketone, t-butyl acetate, xylene,aliphatic hydrocarbons, including hexane, octane, nonane, or decane,wherein the method avoids amine blush or bloom.

Clause 9—The method of clauses 1-8, wherein the coating can be appliedin less than twenty-four hours.

Clause 10—The method of clauses 1-9, wherein the method contains nowashing or sanding of the first curable liquid layer.

Clause 11—The method of clauses 1-10, wherein the quasi-one-dimensionalparticles or quasi-two-dimensional particles are functionalized.

Clause 12—The method of clauses 1-11, wherein the solvent has a boilingpoint less than 200° C.

Clause 13—The method of clauses 1-12, wherein no ketones are used.

Clause 14—The method of clauses 1-13, wherein the quasi-one-dimensionalparticles or quasi-two-dimensional particles are graphitic material,wherein the graphitic material is exfoliated, cut during dispersion, andchemically bound to the at least one polymer or at least one monomer.

Clause 15—The method of clauses 1-13, wherein the quasi-one-dimensionalparticles or quasi-two-dimensional particles are glass flakes, whereinthe glass flakes are silyl coated.

Clause 16—The method of clauses 1-15, wherein volatile organic compoundsare less than 25 weight percent in the coating.

Clause 17—The method of clauses 1-16, wherein the second curable liquidlayer includes at least one polymer or at least one monomer, sacrificialmetal particles, and a solvent.

Clause 18—An anticorrosive-coated substrate including a first curableliquid layer applied to the substrate, the first curable liquid layerhaving a thickness of at least about 100 micrometers, wherein the firstcurable layer includes at least one polymer or at least one monomer,quasi-one-dimensional particles or quasi-two-dimensional particles,sacrificial metal particles, and a solvent, a second curable liquidlayer having a thickness of at least 100 micrometers on top of the firstcurable liquid layer, wherein a percolation threshold of thequasi-one-dimensional particles or the quasi-two-dimensional particlesis reached, wherein the first curable liquid layer and the secondcurable liquid were cured simultaneously.

Clause 19—The substrate of clause 18, wherein the at least one monomeris at least two monomers, wherein one of the at least two monomerscontains at least two epoxy groups, wherein one of the at least twomonomers contains carboxylic anhydride, wherein one of the at least twomonomers contains any combination of the following: amino, thiol,phenolic hydroxyl.

Clause 20—The substrate of clauses 18 or 19, wherein the at least onepolymer forms polyurethane, polyurea, or a mixture of the two, whenallowed to cure, wherein the quasi-one-dimensional particles orquasi-two-dimensional particles are chosen from graphitic particles,carbon nanotubes, graphene, glass flakes, or mica, wherein the solventcontains methyl ethyl ketone, t-butyl acetate, xylene, aliphatichydrocarbons, including hexane, octane, nonane, or decane.

Clause 21—A self-stratifying anticorrosive coating includes a zinc-richepoxy, a curing agent chosen from the group consisting of amines,thiols, phenols, and carboxylic anhydrides, a binding agent chosen fromthe group consisting of aminoalkyl dialkoxysilane, dimethoxysilane, andaminoalkyl trialkoxysilane, a graphitic material, a solvent, and a waterscavenger.

Clause 22—A self-stratifying anticorrosive coating includes sacrificialmetal particles, graphitic material, a first monomer, at least a secondmonomer or at least a first polymer, and a material that prevents thepolymerization of at least one monomer inside the coating.

Clause 23—The coating of clause 22 further includes a curing agent and abinding agent.

Clause 24—The coating of clauses 22 or 23, wherein the at least twodifferent monomers or polymers are chosen from the group consisting ofepoxies, polyurethane, acrylates, methacrylates, vinyl ethers,cycloaliphatic epoxides, oxetanes, epoxides, photopolymers, siloxanes,and polyurea.

Clause 25—The coating of clauses 22-24, wherein the graphitic materialis chosen from the group consisting of single walled carbon nanotubes,double walled carbon nanotubes, multiwalled carbon nanotubes, singlesheet graphene, double sheet graphene, or multi-sheet graphene.

Clause 26—The coating of clauses 22-25, wherein the material thatprevents the polymerization of at least one monomer inside the coatingis a water scavenger chosen from the group consisting of liquid waterscavengers, molecular sieves, silica, metal salts, and metal oxides.

Clause 27—The coating of clauses 22-26, wherein the sacrificial metalparticles are chosen from the group consisting of any metal that hasmore positive redox potential then iron.

Clause 28—The coating of clauses 22-27, wherein the sacrificial metalparticles are chosen from the group consisting of zinc, magnesium,aluminum, and alloys thereof.

Clause 29—The coating of clauses 22-28, wherein the curing agent ischosen from the group consisting of amines, thiols, phenols, andcarboxylic anhydrides, and the binding agent is chosen from the groupconsisting of silanes with at least two alkyl groups. As a non-limitingexample, aminoalkyl dialkoxysilane, dimethoxysilane, and aminoalkyltrialkoxysilane.

Clause 30—The coating of clauses 22-29, wherein the coating furthercomprises a photoinitiator chosen from the group consisting of1-hydroxy-cyclohexyl-phenyl-ketone,2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone,2,2-dimethoxy-2-phenylacetophenone,Bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, triphenyl sulfoniumtriflate, triaryl sulfonium hexafluoroantimonate salts, triarylsulfonium hexafluorophosphate salts, bis(eta5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium,5,7-diiodo-3-butoxy-6-fluorone, 2,4,5,7-tetraiodo-3-hydroxy-6-fluorone,and 2,4,5,7-tetraiodo-3-hydroxy-9-cyano-6-fluorone.

Clause 31—A method for a self-stratifying anticorrosive coating on anassociated substrate including the steps of mixing together a monomer ora polymer, a solvent, a graphitic material, and sacrificial metalparticles, adding a material that prevents polymerization inside thecoating before, and immediately after application on the associatedsubstrate, adding a silane mixture.

Clause 32—The method of clause 31 further comprising the steps of addinga curing agent and applying, in one spraying, the mixture of the monomeror polymer, the solvent, the graphitic material, and the sacrificialmetal particles, the silane mixture, and the curing agent to theassociated substrate, wherein an external effector hydrolyzes the silanemixture creating silicic acid, wherein the silicic acid spontaneouslypolymerizes into siloxane.

Clause 33—The method of clauses 31 or 32, wherein no insulating layer isused.

Clause 34—The method of clauses 31-33 wherein the external effector isambient moisture or photons.

Clause 35—The method of clauses 31-34, wherein the monomer or polymer ischosen from the group consisting of epoxies, acrylates, methacrylates,vinyl ethers, cycloaliphatic epoxides, oxetanes, epoxides,photopolymers, siloxanes, and polyurea.

Clause 36—The method of clauses 31-35, wherein the graphitic material ischosen from the group consisting of single walled carbon nanotubes,double walled carbon nanotubes, multiwalled carbon nanotubes, singlesheet graphene, double sheet graphene, or multi-sheet graphene.

Clause 37—The method of clauses 31-36, wherein the material thatprevents the polymerization inside the coating is a water scavengerchosen from the group consisting of liquid water scavengers, molecularsieves, silica, metal salts, and metal oxides.

Clause 38—The method of clauses 31-37, wherein the sacrificial metalparticles are chosen from the group consisting of any metal that hasmore positive redox potential then iron.

Clause 39—The method of clauses 31-38, wherein the sacrificial metalparticles are chosen from the group consisting of zinc, magnesium,aluminum, and alloys thereof.

Clause 40—The method of clauses 31-39, wherein the coating furthercomprises a photoinitiator chosen from the group consisting of1-hydroxy-cyclohexyl-phenyl-ketone,2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone,2,2-dimethoxy-2-phenylacetophenone,Bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, triphenyl sulfoniumtriflate, triaryl sulfonium hexafluoroantimonate salts, triarylsulfonium hexafluorophosphate salts, bis(eta5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium,5,7-diiodo-3-butoxy-6-fluorone, 2,4,5,7-tetraiodo-3-hydroxy-6-fluorone,and 2,4,5,7-tetraiodo-3-hydroxy-9-cyano-6-fluorone, wherein the curingagent is chosen from the group consisting of amines, thiols, phenols,and carboxylic anhydrides, and the binding agent is chosen from thegroup consisting of aminoalkyl dialkoxysilane, dimethoxysilane, andaminoalkyl trialkoxysilane.

The various aspects have been described, hereinabove. It will beapparent to those skilled in the art that the above methods andapparatuses may incorporate changes and modifications without departingfrom the general scope of the present teachings. It is intended toinclude all such modifications and alterations insofar as they comewithin the scope of the appended claims or the equivalents thereof.Although the description above contains much specificity, this shouldnot be construed as limiting the scope of the present teachings, but asmerely providing illustrations of some of the aspects of the presentteachings. Various other aspects and ramifications are possible withinits scope.

Furthermore, notwithstanding that the numerical ranges and parameterssetting forth the broad scope of the present teachings areapproximations, the numerical values set forth in the specific examplesare reported as precisely as possible. Any numerical value, however,inherently contain certain errors necessarily resulting from thestandard deviation found in their respective testing measurements.

The invention claimed is:
 1. A method of coating an associated substratewith an anticorrosive coating, the method comprising the steps of:applying a first curable liquid layer to the associated substrate, thefirst curable liquid layer having a thickness of at least about 100micrometers, wherein the first curable layer comprises: at least onepolymer or at least one monomer; quasi-one-dimensional particles orquasi-two-dimensional particles; sacrificial metal particles; and asolvent in an amount such that a percolation threshold of thequasi-one-dimensional or quasi-two-dimensional particles is not reached;evaporating between about 1% and 20% of the solvent from the firstcurable liquid layer to provide a modified first curable liquid layerwherein the percolation threshold is reached and the modified firstcurable liquid layer has a viscosity that is more than 50% greater thana viscosity of the first curable liquid layer; and applying a secondcurable liquid layer having a thickness of at least about 100micrometers on the top of the modified first curable liquid layer. 2.The method of claim 1, wherein the method further comprises the step of:allowing the modified first curable liquid layer and the second curableliquid layer to cure simultaneously.
 3. The method of claim 1, whereinthe at least one monomer is at least two monomers, wherein one of the atleast two monomers contains at least two epoxy groups, wherein one ofthe at least two monomers contains carboxylic anhydride, wherein one ofthe at least two monomers contains any combination of the following:amino, thiol, phenolic hydroxyl.
 4. The method of claim 3, wherein thequasi-one-dimensional particles have a concentration between about 0.1weight percent and about 2.0 weight percent in the first curable liquidlayer, or the quasi-two-dimensional particles have a concentrationbetween about 2.0 weight percent and about 20 weight percent in thefirst curable liquid layer.
 5. The method of claim 1, wherein theanticorrosive coating absorbs substantially no water or carbon dioxide.6. The method of claim 1, wherein the first curable liquid layercontains quasi-one-dimensional particles and quasi-two-dimensionalparticles.
 7. The method of claim 1, wherein the at least one polymerforms polyurethane, polyurea, or a mixture of the two, when allowed tocure.
 8. The method of claim 1, wherein the quasi-one-dimensionalparticles or quasi-two-dimensional particles are chosen from graphiticparticles, carbon nanotubes, graphene, glass flakes, or mica, whereinthe solvent contains methyl ethyl ketone, t-butyl acetate, xylene,oraliphatic hydrocarbons, and wherein the method avoids amine blush orbloom.
 9. The method of claim 8, wherein the quasi-one-dimensionalparticles or quasi-two-dimensional particles are graphitic material,wherein the graphitic material is exfoliated, cut during dispersion, andchemically bound to the at least one polymer or at least one monomer,and wherein the aliphatic hydrocarbons are chosen from hexane, octane,nonane, or decane.
 10. The method of claim 1, wherein the anticorrosivecoating can be applied in less than twenty-four hours.
 11. The method ofclaim 1, wherein the method contains no washing or sanding of the firstcurable liquid layer.
 12. The method of claim 1, wherein thequasi-one-dimensional particles or quasi-two-dimensional particles arefunctionalized.
 13. The method of claim 1, wherein the solvent has aboiling point less than 200° C.
 14. The method of claim 1, wherein noketones are used.
 15. The method of claim 1, wherein volatile organiccompounds are less than 25 weight percent in the anticorrosive coating.16. The method of claim 1, wherein the second curable liquid layercomprises: at least one polymer or at least one monomer; sacrificialmetal particles; and a solvent.
 17. A method of coating an associatedsubstrate with an anticorrosive coating, the method comprising the stepsof: applying a first curable liquid layer to the associated substrate,the first curable liquid layer having a thickness of at least about 100micrometers, wherein the first curable layer comprises: at east onepolymer or at east one monomer; quasi-one-dimensional particles orquasi-two-dimensional particles; sacrificial metal particles; and asolvent in an amount such that a percolation threshold of thequasi-one-dimensional or quasi-two-dimensional particles is not reached;allowing at east about 1% of the solvent to evaporate to thereby providea modified first curable liquid layer wherein the percolation thresholdof the quasi-one dimensional particles or the quasi-two-dimensionalparticles is reached and a viscosity of the modified first curableliquid layer is more than 50% greater than a viscosity of the firstcurable liquid layer; and applying a second curable liquid layer havinga thickness of at east about 100 micrometers on the top of the modifiedfirst curable liquid layer.